Vehicle comprising a battery drive and a method for operating a vehicle of this type

ABSTRACT

Electrically driven passenger transport vehicles are supplied with energy by an external electric supply network. If the external energy supply fails, vehicles of this type require special auxiliary devices that do not rely on the supply network, for example rely on auxiliary vehicles, in order to move said vehicles again. A vehicle can move independently during a failure of the external energy supply, by switching the electric drive of said vehicle to a battery drive.

The present invention relates to a vehicle having an electric drive which is supplied by an external electric supply system, and at least one battery and a method for operating such a vehicle, and a method for retrofitting a vehicle with an electric drive which is supplied by an external electric supply system.

Means of urban local and regional passenger transportation such as trams or trolleybuses are generally not moved on a separate roadway but instead are operated together with the individual traffic on the same roadway, generally a road. These means of transportation are usually electrically driven and supplied with electric power via contact lines, for example overhead lines. When the power supply fails as a result of technical failure, for example a rupture of a line or when there is a defect in the current collector, etc., there is the considerable risk of the traffic being impeded since the vehicle can no longer move independently, which is very critical in urban situations and can result in considerable financial loss as a result of congestion of individual traffic. Basically, such means of transportation cannot be operated independently without an external power supply, which can lead to problems in certain situations, for example starting up when the vehicle is stationary with current collectors under section isolators, or when there is a power failure. It is also impossible to carry out voltageless shunting movements in the depot but instead expensive auxiliary vehicles are always necessary.

From the prior art, what are referred to as hybrid vehicles are known for this purpose, said vehicles having different power supplies between which it is possible to switch when necessary and which can be used to supply the drive of the vehicle when necessary. These are respectively fully functional power supply systems or a fully functional drive with which the vehicle can be moved at least over a certain time period without limiting the load or speed. Such a vehicle is known, for example, from WO 93/04887 A1 and WO 00/77918 A1. Since the power supply systems in these vehicles have to be at least approximately equivalent, they of course also have to be given equivalent dimensions, which increases the costs for the backup drive, and thus for the vehicle.

The present invention is therefore based on the object of specifying a vehicle which can be moved independently by means of an auxiliary supply system, without additional external drives, both in the normal operating mode, that is to say while the vehicle is being supplied via an external electric supply system, and when the external supply system fails.

The vehicle and method according to the invention are characterized in that the electric drive is supplied by the battery when the external electric supply system is disconnected or fails, the supply voltage of the battery being at maximum 25%, preferably less than 10%, of the external supply system voltage. This ensures that when the external supply is disconnected the vehicle can be moved independently, even without additional auxiliary vehicles or without an additional auxiliary drive. In particular, significantly fewer auxiliary vehicles which are independent of contact lines are necessary, which considerably reduces the costs for the operator of the vehicles. Attempts in practice have shown that in the operating mode with the battery approximately 30% of the normal traction force can be achieved, which is at any rate sufficient to accelerate somewhat from a standstill a typical tram vehicle having a weight of several tons, for example approximately 45 t, and to move it along at a snail's pace.

This vehicle according to the invention can be implemented almost exclusively with the already existing standard components, as a result of which the technical implementation is easy and the additional costs are negligible.

Furthermore, inexpensive standard batteries, for example with a rated voltage of 24 V, can thus be used.

It is especially advantageous if the battery which is provided for supplying the on-board supply system of the vehicle, for example the electronic control system of the vehicle, etc., in the normal operating mode is used for supplying the electric drive. Any vehicle generally has an on-board battery which is used to supply the fundamental control functions of the vehicle, such as, for example, the general control system, the raising and lowering of the current collector, the vehicle lighting system, etc. This existing battery can then be used directly as a supply for the electric drive without providing additional further batteries.

If at least one circuit breaker is provided by means of which the electric drive can be disconnected from the external electric supply system and connected to the battery, the switching-over from the external power supply to the battery supply can be carried out particularly easily.

An electric drive which is embodied as a power unit, in particular a power inverter, with an electric motor, in particular an asynchronous motor is suitable in an especially advantageous fashion for this specific application. When the supply changes, all that is necessary is to actuate the power inverter differently, everything else can remain unchanged.

When the electric supply of the drive is changed, the electric relationships of the electric drive, which are advantageously taken into account by means of a control unit for actuating the electric drive, change. A battery (for example with a 24 V rated voltage) generally has a significantly lower available voltage than an electric supply system (for example a 600 V supply system). As a result, the voltage drops at the semiconductors such as diodes and transistors of the power unit, as well as offset faults in the measurement of the voltage in the intermediate circuit of the power unit, have to be taken into account in order to obtain the magnetic flux which is necessary for the drive. This can be implemented very advantageously if the control unit is designed to compensate the fault in the magnetization of the electric motor of the electric drive. As a result, the control system is capable of ensuring the optimum magnetization, even under completely changed electrical conditions.

The use of the stored power which is available in the battery is advantageously optimized by means of a battery management unit.

This optimization is favorably carried out with respect to a power limiting means, ensuring that the permitted battery current is not exceeded, and/or a setpoint torque limiting means, ensuring both traction up to the point where the battery is exhausted, and residual availability of the control voltage at the vehicle.

It is in this case also necessary to take into account the fact that as a result of the internal voltage drop of the battery a severe reaction of the battery current on the voltage of the electric motor occurs (“soft” voltage supply in contrast to the relatively rigid external electric supply system) which is also dependent on the charge state of the battery. As a result, the dynamics of the drive change.

The method for retrofitting a vehicle with an electric drive is characterized in that a circuit breaker is installed which is connected, on the one hand, to at least one battery which is present or, if appropriate, to be retrofitted, and, on the other hand, to the power unit, for example a power inverter, of the electric drive, and the control unit is replaced or updated as necessary. Furthermore, a separate battery management unit is advantageously installed in order to be able to use the battery in an optimum way, it being also possible to integrate this battery management unit into the control unit.

Since, for the most part, except for the circuit breaker, only already present components of the vehicle are used, existing vehicles can also be retrofitted without a large degree of effort. As a rule, only one switch has to be installed and the control software and/or hardware updated in order to be able to cover even the failure of the supply to the drive via the batteries.

The invention which forms the subject matter will be described with reference to the exemplary FIGS. 1 and 2 which are not restrictive and which show a specific exemplary embodiment,

FIG. 1 showing a schematic illustration of a vehicle according to the invention, and

FIG. 2 showing a schematic circuit diagram of the electric drive of the vehicle.

An electrically driven vehicle 1 according to FIG. 1, here a tram, is supplied with electric power via an overhead line 4 by means of an external electric supply system, here a 600 V supply system, (not illustrated in more detail). The electric power is tapped in a sufficiently known fashion by means of a current collector 2. The electric drive 3 in this configuration is composed of, for example, as shown in FIG. 2, an electric motor 9, here an asynchronous motor, and may also, if necessary, contain a transmission as well as a power inverter 13 as a power unit 8 which actuates the electric motor 9. A control unit 7 controls the entire electric drive 3. Furthermore, as is sufficiently known, on-board supply system batteries 5, here 24 V batteries, are provided which supply important parts of the vehicle 1 such as the electronic control system or the basic lighting system of the vehicle 1, etc., with electric power independently of the external supply system.

The vehicle 1 which is described above is, of course, only to be considered as an example. In particular, the individual components can be arranged at any other desired locations on the vehicle 1, for example instead of overhead lines 4 it would also be possible to provide lateral sliding contacts, and the individual components can of course also be provided multiply, for example, a vehicle 1 can be provided with two drives 3. In many embodiment variants the drive 3 is also accommodated directly in the chassis of the vehicle 1.

In the normal operating mode, the electric drive 3 of the vehicle 1 is supplied with electric power by the external electric supply system. If appropriate, the batteries 5 only supply the electronic control system and other components of the vehicle 1 here, and they can be charged via the external electric supply system when necessary.

If the external supply system fails, for example owing to a line break or a power failure, or if the vehicle 1 is to be operated in a range without an external supply system, for example in a depot, in the past, auxiliary vehicles which are independent of a contact line have previously been necessary in order to be able to move the vehicle.

The vehicle 1 according to the invention in FIG. 2 has a circuit breaker 6 which, in such cases, connects the power inverter 13 of the electric drive 3 to the on-board supply system batteries 5. The vehicle 1 is therefore no longer supplied with electric power by the external supply system but rather by the already present on-board supply system batteries 5.

As a result of the significantly lower supply voltage, here 24 V instead of 600 V, for which the drive 3 is configured, completely different electrical conditions arise during switching over, for example parasitic effects, which could be compensated by the control unit 7, come to bear dramatically at a low voltage. For example, the voltage drops at the transistors and diodes of the power inverter 13 could be taken into account and the fault in the magnetization of the electric motor 9 compensated in order to obtain the magnetic flux which is necessary for operation. Furthermore, a separate battery management unit, which could also be the control unit 7, can be provided since the batteries 5 have only a restricted amount of power which should be utilized in an optimum way. For this purpose, on the one hand, a power limiting means could be provided since each battery should be loaded only with a specific maximum battery current, and in order to prevent the battery 5 becoming exhausted, and on the other hand, a maximum drive torque is to be obtained. The battery management system ensures both traction to the point where the battery 5 is exhausted, and residual availability of the control voltage at the vehicle 1.

It is, of course, conceivable to use any desired number of the present on-board supply system batteries 5 to supply the electric drive 3, or else to equip a plurality of drives 3 of the vehicle 1 in this way.

In this specific exemplary embodiment, the power unit 8 is composed of a power inverter 13 which is connected to an intermediate circuit capacitor 12 and to the external supply system via a main contactor 10 and a supply system reactor 11. In the event of a failure, the main contactor 10 is opened by means of the control unit 7, and the circuit breaker 6 is closed, as a result of which the power unit 8 is thus supplied by the battery 5. The grounding is carried out in this example by means of a grounding earth contact 14.

However, basically, any desired other circuits are also possible, for example a two-pole embodiment of the circuit breaker 6 if the battery circuit is grounded differently, or the use of some other power unit 8 in which the main contactor 10 and supply system reactor 11 are not integrated in the power converter, etc. 

1. A vehicle having an electric drive, the drive is supplied by an external electric supply , and the drive is operable by at least one battery located at the vehicle and having a rated voltage different than the voltage of the external electric supply system; the electric drive is configured to operate with the voltage of the external electric supply system and can be supplied by and is configured to operate the battery when the external electric supply system is disconnected or fails, and a control unit for actuating the electric drive and the control unit takes into account the changed electrical relationships of the electric drive caused by a changed supply voltage in the battery operating mode.
 2. The vehicle as claimed in claim 1, wherein the vehicle has an on-board supply system and the battery is operable for supplying the on-board supply system of the vehicle in a normal operating mode of the electric drive during the drive being supplied by an external electric supply system.
 3. The vehicle as claimed in claim 1 further comprising at least one circuit breaker connected to the electric drive. to the external electric supply system and to the battery and the circuit breaker is operable so that the electric drive can be disconnected from the external electric supply system and connected to the battery, and vice versa.
 4. The vehicle as claimed in claim 1, wherein the electric drive comprises a power unit, and an electric motor (9), connected to the power unit.
 5. The vehicle as claimed in claim 4, wherein the control unit is operable to compensate fault in the magnetization of the electric motor of the electric drive.
 6. The vehicle as claimed in claim 1, further comprising a battery management unit connected with the battery and operable for optimizing the use of stored power which is available in the battery.
 7. The vehicle as claimed in claim 6, further comprising a power limiting device in the battery management unit.
 8. The vehicle as claimed in claim 6, further comprising a setpoint torque limiting device in the battery management unit.
 9. A method for operating a vehicle having an electric drive operable by an external electric supply system and the electric drive is configured with respect to the voltage of the external electric supply system, the method comprising switching the electric drive over to a battery operating mode when the external electric supply system is disconnected or fails, while adjusting the electric drive to take into account the changed electrical relationships of the electric drive which are brought about by the changed supply voltage in the battery operating mode to actuate the electric drive.
 10. The method as claimed in claim 9, further comprising supplying an on-board supply system of the vehicle by the battery in the normal operating mode.
 11. The method as claimed in claim 9, further comprising compensating the fault in the magnetization of the electric motor of the electric drive.
 12. The method as claimed in claim 9 further comprising optimizing use of stored power available in the battery.
 13. The method as claimed in claim 12, wherein the power which is extracted from the battery is limited and use of the limited power is optimized.
 14. The method as claimed in claim 12, further comprising limiting a setpoint torque of the electric motor of the electric drive.
 15. (canceled)
 16. A method for retrofitting a vehicle having an electric drive which is supplied by an external electric supply system, the method comprising: connecting a circuit breaker located on the vehicle to at least one electric battery and, to a power unit of the electric drive and replacing or updating a control unit for actuating the power unit , of the electric drive.
 17. The method as claimed in claim 16, further comprising installing a battery management unit which optimizes the use of the battery.
 18. A vehicle as claimed in claim 1, wherein the electric drive is operable by a 600V supply system and the battery has a 24V rated voltage.
 19. A vehicle as claimed in claim 1, wherein the supply of the battery is at maximum 25% of the external supply system voltage.
 20. A vehicle as claimed in claim 1, wherein the supply of the battery is less than 10% of the external supply system voltage.
 21. The vehicle as claimed in claim 4, wherein the power unit comprises a power inverter and the electric motor is an asynchronous motor.
 22. The vehicle as claimed in claim 7, further comprising a setpoint torque limiting device in the battery management unit.
 23. A method as claimed in claim 9, wherein the supply voltage of the battery is selected with a maximum 25% of the external supply system voltage.
 24. A method as claimed in claim 9, wherein the supply voltage of the battery is selected with less than 10% of the external supply system voltage.
 25. A method as claimed in claim 10, wherein the on-board supply system is the electronic control system of the vehicle.
 26. A method as claimed in claim 12, wherein the use of the stored power available to the battery is optimized with respect to power utilization by the electric drive.
 27. A method as claimed in claim 16, wherein the power unit comprises a power inverter. 